1. Field of the Invention
The present invention relates to toner to be used in an image forming method such as an electrophotographic method, an electrostatic recording method, an electrostatic printing method, or a recording method of toner jet system, and to an image forming method as well as an apparatus unit using the above described toner, and the present invention relates to a toner manufacturing method to efficiently proceed with grinding and classification of toner with small particle size having bonding resin and to obtain toner having sharp particle density distribution efficiently.
2. Related Background Art
As electrophotographic method, a number of methods such as those described in U.S. Pat. No. 2,297,691 specification, Japanese Patent Publication No. 42-23910 specification and Japanese Patent Publication No. 42-24748 specification are known. In general, the above described method utilizes photoconductive substance to form electrostatic charge latent image onto a photosensitive body with a variety of means, and subsequently to develop the latent image with toner, to transfer a toner image onto a transferring material such as sheet paper in accordance with necessity, and afterward to undergo fixing by means of heating, pressing, heat-pressing or solvent steam so as to obtain a toner image.
In recently years, complying with multifunctionization of photocopiers and printers, high-fidelity of copied image, and moreover, high speeding, performance required to toner becomes severer and for instance a particle size of toner is micronized into a micro particle and as particle density distribution the one that does not contain coarse particles but provides with sharpness with less supermicro powders is required.
Among the above described steps, in the case of having transferred an toner image onto a transferring At material from the photosensitive body, there exists residual toner subject to transferring on the photosensitive body.
In order that continuous copying is implemented swiftly, the residual toner on this photosensitive body needs to be cleaned off. Moreover, the recovered residual toner is putted into a container installed inside the main body or into-a collection box, and afterwards is abandoned or is returned to a developing container again and used in a developing step for recycling.
As approach to ecological issues, a design on the main body in which a recycling system is installed inside the main body as waste tonerless system will be necessary.
However, in order to attain multifunctionization of photocopiers and printers, high-fidelity of copied image, and moreover, high speeding, a recycling system on a fairly large scale gets necessary inside a main body, resulting in that an image forming apparatus itself such as a photocopier as well as a printer will get large and will not cope with miniaturization from a point of view of space saving. Moreover, there are no differences in a system in which waste toner is contained in a container installed inside a main body or in a recovery box and a system in which a photosensitive body and the above described waste toner collecting portion are integrated.
In order to comply with them, it is necessary to improve a transferring ratio at the time when a toner image is transferred onto a transferring material from the photosensitive body so that the waste toner is reduced.
In Japanese Patent Application Laid-Open No. 9-26672 specification, such a method is disclosed for improving transferring efficiency by including a transferring efficiency improver having a mean particle size of 0.1 to 3 xcexcm and hydrophobic silica micro powder in toner so that toner volumetric resistant is reduced and the transferring efficiency improver forms a thin film layer on a photosensitive body. However, because of particle density distribution in the toner manufactured by grinding method it is difficult to attain a uniform effect for all particles, and further improvement is needed.
As a method to improve transferring efficiency by providing spherical shape of toner particles, toner by means of manufacturing methods such as spray granulation method, solution dissolution method, polymerization method are disclosed in Japanese Patent Application Laid-Open No. 3-84558 specification, Japanese Patent Application Laid-Open No. 3-229268 specification, Japanese Patent Application Laid-Open No. 4-1766 specification, and Japanese Patent Application Laid-Open No. 4-102862 specification. However, these toner manufacturing methods not only require equipment on a fairly large scale, but also give rise to such a problem that toner particles, which have weak spherical shape, manage to pass through during a cleaning step, and therefore cannot be regarded as preferable method in the case where only transferability improvement is pursued.
As manufacturing means in general, binding resin for fixing it onto a material to be transferred to, various kinds of coloring agent for creating color taste of toner, and electrical charge control agent for giving particles charge are used as raw material, and in so-called mono-component developing as shown in Japanese Patent Application Laid-Open No. 54-42141 Specification and Japanese Patent Application Laid-Open No. 55-18656 Specification, in addition thereto various magnetic materials are used for giving toner itself carrying capacity, and moreover, if necessary, another additives, for example, mold release agent and flowability giving agent and the like are added and dry mixed, and then, there material are melt kneaded with a kneading apparatus for general use such as a roll mill and an extruder cooled and solidified, and thereafter the kneaded product is grinded with various grinding apparatus such as a jet stream mill and a mechanical impact mill or the like, and the obtained coarse ground product is introduced into various wind force classifiers for classification, thereby classified product falling within a particle size necessary as toner is obtained, and moreover, when as necessary, streamer or sliding agent, etc. is added from outside for dry mixing to get toner to be served for image forming. In the case of toner to be used for two component development, every kind of magnetic carrier is mixed with the above described toner, and thereafter is served for image forming.
As described above, in order to obtain toner particles being micro particles, a method shown in a flow chart in FIG. 10 is generally adopted.
While toner coarse ground product is continuously or successively supplied to first dispersion means, coarse powder comprising a group of coarse particles as main component not smaller than dispersed regular grain size is conveyed to grinding means to undergo grinding and thereafter is circulated back to the first classification means again.
Toner pulverized product with particles within another regular grain size and particles not larger than regular grain size as main component is conveyed to second classification means and undergoes classification into medium size powder with a group of particles of regular grain size as main component and into fine powder with a group of particles not larger than the regular grain size as main component. However, the toner undergoing processing into micro particles intensifies electrostatic aggregation among particles, and since the toner that originally should have been conveyed to the second classification means is circulated to the first classification means again, fine powder as well as superfine powder having undergone over-grinding is brought about.
As grinding means, a variety of grinding apparatuses are used, but for grinding of toner coarse ground product with a binding resin as main substance, a jet stream mill using jet stream, in particular an impact airflow mill shown in FIG. 13 is used.
An impact airflow mill shown using highly-pressured gas such as jet stream conveys a powder raw material with a jet stream, spray it from an outlet port of an acceleration duct so that the powder raw material is made to crash onto a crashing plane on a crashing member provided to face an open plane in the outlet port of an acceleration duct and the powder raw material undergoes grinding with impact thereof.
For example, in an impact mill shown in FIG. 13, an impact member 164 is provided so as to face an outlet port 163 of an accelerating tube 162 that is brought into connection with a highly-pressured gas supplying nozzle 161, and a highly-pressured gas supplied to the accelerating tube 162 absorbs a powder raw material from a powder raw material supplying port 165 brought into communication in the accelerating tube 162 to inside the accelerating tube 162 so that the powder raw material is sprayed together with the highly-pressured gas to undergo crashing onto the impact surface 166 of the impact member 164 and to undergo grinding with that impact, and a ground product is discharged from a grinding chamber 168 via a ground product exit 167.
However, the above described impact airflow mill is configured so that a powder raw material is sprayed together with a highly-pressured gas to crash onto an impact surface of an impact member, and undergoes grinding with an impact thereof, bringing about ground toner being an angular product with indeterminate forms, and in addition, in order to produce toner with a small powder size a quantity of air is required. Therefore, power consumption is extremely abundant, and a problem remains on an aspect of energy cost.
Japanese Patent Application Laid-Open No. 2-87157 specification discloses a method for improving transferring efficiency by modifying shape as well as surface characteristics of a toner manufactured by a grinding method with mechanical impact (hybridizer). However, this method cannot be considered as a favorable method since a processing step comes further after grinding, so toner production performance as well as processing causes toner surface to approach a state without any roughness and requires improvement, etc. on a developing surface.
Especially, in recent years, in order to comply with environmental issues, energy saving on apparatuses is called for.
In the case where toner having weight mean particle size of 8 xcexcm and percentage of volume less than 4.00 xcexcm is not more than one percent is obtained in classifying means, a raw material undergoes grinding for classification to reach a predetermined mean particle size with grinding means such as an impact airflow mill equipped with classifying mechanism in order to remove those in coarse powder and a ground product after the coarse powder is removed is applied to another classifying machine to remove micro powder and obtains a desired medium powder.
Incidentally, weight mean particle size referred to herein is data measured with Coulter Counter Type TA II or Coulter Multiciser Type II manufactured by Coulter Electronics Ltd. to be described later adopting 100 xcexcm aperture.
As concerns such a conventional method, a group of particles subject to complete removal of a group of coarse particles having a grain size not less than a certain regular grain size must be conveyed to the second classifying means for removing micro powder, and therefore load on grinding means gets large with less process quantity, bringing about a problem. Removal of a group of coarse particles having a grain size not less than a regular grain size tends to cause over-grinding, and as a result thereof, a phenomena such as drop in yield in a second classifying means in order to remove micro powder in a next step takes place easily as a problem.
As for a second classifying means for removing micro powder, a aggregated product configured by super micro particles may be created, and it is impossible to remove the aggregated product as micro powder. In that case, the aggregated product is mixed into a final good, resulting in difficulty in obtaining a good having a fine grain size distribution. Moreover, the aggregated product is disintegrated to become super micro particles so as to become one of causes for decreasing image quality.
As for such a second classifying means for removing micro powder, various kinds of airflow classifier as well as methods thereon are proposed. Among them, some classifying machines utilize propellers and some classifying machines do not have movable parts. Among them, as classifying means without any movable parts, there exist a fixed wall centrifugal classifier and an inertial classifier. Such a classifying machine that utilizes inertia force is proposed in Japanese Patent Publication No. 54-24745 specification, Japanese Patent Publication No. 55-643 specification, and Japanese Patent Application Laid-Open No. 63-101858 specification.
These airflow classifiers, as shown in FIG. 8, sprays powder into a classifying range together with airflows at a high speed from a supply nozzle having an opening in a classifying range of a classifying machine chamber into the classifying range, and inside the classifying chamber centrifugal force of a curve airflow flowing along a Coanda block 145 separates it into coarse powder, medium powder and fine powder and edges 146 and 147 implement classification in coarse powder, medium powder and fine powder.
A conventional classifying apparatus 57 introduces micro grinding raw material from a raw material supply nozzle so that powder flowing inside pyramid tubes 148 and 149 tends to flow straight in parallel along the tube walls with a propulsion force. However, when the raw material is introduced from an upper portion inside the above described raw material supply nozzle, it is roughly separated into an upper stream and into a lower stream, and the upper stream contains light fine powder much while the lower stream is apt to contain heavy coarse powder much, and each particle flows independently so that depending on a location to be introduced into the classifying machine chamber different trances are drawn or the coarse powder interrupts traces of the fine powder and therefore a limit in improvement of classification accuracy is brought about and accuracy in classification on powder containing coarse particles with sizes not less than 20 xcexcm was apt to drop.
In general, a number of different qualities are required to toner, and in order to give such required qualities thereto, raw materials for use as well as a manufacturing method are often important. In the classification step of toner, particles subject to classification are required to have sharp grain size distribution. In addition, it is desired that quality toner is created at low costs, efficiently and constantly.
Moreover, for improvement in image quality in a photocopier or a printer, such toner is required that undergoes micro grinding in terms of powder size and does not contain coarse particles in terms of grain size distribution but is sharp with less super fine powder. In general, influence of forces between particles gets larger as a matter gets smaller, and it is applicable to resin and toner, which is eventually with micro powder size so that aggregation performance between particles will get more intensive.
In particular, in case of obtaining toner having sharp grain size distribution with weight mean size of not more than 12 xcexcm, a conventional apparatus as well as method brings about drop in classification yield. Moreover, in case of obtaining toner having sharp grain size distribution with weight mean size of not more than 8 xcexcm, in particular, a conventional apparatus as well as method brings about drop in classification yield but also is apt to cause the toner to contain a quantity of super fine powder.
Even if a desired product having fine grain size distribution can be obtained under the conventional system, steps get complicated, bringing about drop in classification yield, worsening production efficiency, and heightening costs. This tendency gets more remarkable as a predetermined grain size gets smaller.
A toner manufacturing method as well as apparatus that uses first classification means, grinding means and multi-section classifying means as second classifying means is proposed in Japanese Patent Application Laid-Open No. 63-101858 Specification (correspondent with U.S. Pat. No. 4,844,349). However, a method as well as an apparatus in order that toner with weight mean size of not more than 8 xcexcm is created constantly and efficiently is longed for.
Moreover, toner that has undergone micro grinding will contain relatively many coloring agents (magnetic material) in the toner, resulting in difficulty in maintaining toner""s low temperature fixing performance and as for developing performance will get severer restriction than in conventional one, too.
That is, it is a current status that toner having undergone improvement in transfer efficiency and having good fixing performance and high developing performance for reducing transferring residual toner on a photosensitive body that will become waste toner inclusive of productivity of the toner itself is not realizable.
An object of the present invention is to provide toner that has solved the above described problems, a method for manufacturing toner, image forming method as well as an apparatus unit using the above described toner.
An object of the present invention is to provide toner giving rise to less waste toner with high transferring efficiency and an image forming method as well as an apparatus unit using the above described toner.
An object of the present invention is to provide toner having good low temperature fixing performance and an image forming method as well as an apparatus unit using the above described toner.
An object of the present invention is to provide toner capable of maintaining good developing performance toward micro pulverizing and an image forming method as well as an apparatus unit using the above described toner.
An object of the present invention is to provide toner having high productivity that can be produced easily with a pulverizing method and an image forming method as well as an apparatus unit using the above described toner.
An object of the present invention is to provide such a method for manufacturing toner that is efficient and uses pulverizing classification system of powder with extremely less power consumption in addition to simple apparatus configuration and with less energy costs.
An object of the present invention is to provide such a method for manufacturing toner that makes toner having fine particle size distribution capable of being efficiently produced.
An object of the present invention is to provide such a method for manufacturing toner that enables toner having sharp particle size distribution of weight mean size of not more than 10 xcexcm (moreover, not more than 8 xcexcm) to be efficiently produced.
An object of the present invention is to provide toner comprising:
At least a bonding resin and a coloring agent, Wherein the above described toner has the following characteristics (i) to (iv):
(i) its weight mean particle size is 5 xcexcm to 12 xcexcm;
(ii) not less than 90% (in terms of cumulative value based on the number of particles) of particles of not less than 3 xcexcm has a circularity xe2x80x9caxe2x80x9d of not less than 0.900 given by the following equation (1):
Circularity a=Lo/Lxe2x80x83xe2x80x83(1)
xe2x80x83[In the equation, Lo denotes a periphery length of a circle having the same projected area as a particle image and L denotes a periphery length of the particle image];
(iii) Relationship between a cut ratio Z and a weight mean size X of the above described toner fulfills the following equation (2):
Cut ratio Zxe2x89xa65.3xc3x97Xxe2x80x83xe2x80x83(2)
[Incidentally, the cut ratio Z is a value calculated with a following equation (3):
Z=(1xe2x88x92B/A)xc3x97100xe2x80x83xe2x80x83(3)
Wherein A is a particle density (the number of particles/xcexcl) of all measured particles measured with a flow type particle image analyzer and B is a particle density (the number of particles/xcexcl) of measured particles having a circular equivalent size of not less than 3 xcexcm.]; and
(iv) Relationship between a cumulative value based on the number of particles Y of particles having a circularity of not less than 0.950 and a weight mean size X fulfills the following equation (4):
Yxe2x89xa7exp 5.51xc3x97Xxe2x88x920.645xe2x80x83xe2x80x83(4)
[Incidentally, the weight mean size X is 5.0 to 12.0 xcexcm.]
An object of the present invention is to provide a process for producing a toner, comprising the steps of:
melt-kneading a mixture containing at least a bonding resin and a coloring agent to obtain a kneaded product;
cooling the obtained kneaded product and thereafter roughly pulverizing the cooled product with grinding means to obtain a roughly pulverized product;
introducing a powder raw material of the resulting pulverized product into a first metering feeder and introducing a predetermined quantity of powder raw material from the above described metering feeder into a mechanical mill, wherein the above described mechanical mill is provided at least with a rotor mounted on a center rotary shaft, a stator disposed around the rotor with a constant distance from surfaces of the above described rotor being maintained, a powder introducing orifice for introducing a powder raw material, and a powder discharging orifice for discharging ground powder and is so configured that an annular space formed by maintaining the distances is in an airtight state;
finely pulverizing the powder raw material in order to obtain a finely pulverized product by rotating the above described rotor of the above described mechanical mill at high speed;
discharging the finely pulverized product from mechanical mill and introducing it into a second metering feeder so that from the above described second metering feeder a predetermined quantity of finely pulverized product is introduced into a multisegment airflow classifier for classifying by airflow the powder by utilizing cross airflows and Coanda effect; and
classifying the finely pulverized product into at least fine powder, medium powder and coarse powder inside the above described multisegment airflow classifier;
wherein the classified coarse powder is mixed with the above described powder raw material to be introduced into the above described mechanical mill in the above described pulverization step for and the toner is produced from the classified medium powder.
An object of the present invention is to provide an image forming method comprising:
a charging step to charge a latent image holding body;
a latent image forming step to form an electrostatic latent image onto the charged latent image holding body;
a developing step to develop the above described electrostatic latent image with toner and to form a toner image;
a transferring step to transfer the developed toner image onto a recording material via an intermediate transfer member or otherwise directly; and
a fixing step to fix the toner image transferred onto the recording material onto the above described recording material with fixing means:
wherein the above described toner at least has bonding resin and a coloring agent and has the following characteristics (i) to (iv):
(i) its weight mean particle size is 5 xcexcm to 12 xcexcm;
(ii) not less than 90%, (in terms of cumulative value based on the number of particles) of particles of not less than 3 xcexcm has a circularity xe2x80x9caxe2x80x9d of not less than 0.900 given by the following equation (1):
Circularity a=Lo/Lxe2x80x83xe2x80x83(1)
xe2x80x83[In the equation, Lo denotes a periphery length of a circle having the same projected area as a particle image and L denotes a periphery length of the particle image];
(iii) Relationship between a cut ratio Z and a weight mean size X of the above described toner fulfills the following equation (2):
Cut ratio Zxe2x89xa65.3xc3x97Xxe2x80x83xe2x80x83(2)
xe2x80x83[Incidentally, the cut ratio Z is a value calculated with a following equation (3):
Z=(1xe2x88x92B/A)xc3x97100xe2x80x83xe2x80x83(3)
xe2x80x83Wherein A is a particle density (the number of particles/xcexcl) of all measured particles measured with a flow type particle image analyzer and B is a particle density (the number of particles/xcexcl) of measured particles having a circular equivalent size of not less than 3 xcexcm]; and
(iv) Relationship between a cumulative value based on the number of particles Y of particles having a circularity of not less than 0.950 and a weight mean size X fulfills the following equation (4):
Yxe2x89xa7exp 5.51xc3x97Xxe2x88x920.645xe2x80x83xe2x80x83(4)
[Incidentally, the weight mean size X is 5.0 to 12.0 xcexcm]
An object of the present invention is to provide an apparatus unit detachably mountable on a main assembly of an image forming apparatus comprising:
Toner for developing an electrostatic latent image;
a toner container for holding the above described toner;
a toner carrier for carrying and conveying toner held in the above described toner container; and
a toner layer thickness controlling member to control layer thickness of the toner carried by the above described toner carrier:
wherein the above described toner at least has bonding resin a coloring agent and has the following characteristics (i) to (iv):
(i) its weight mean particle size is 5 xcexcm to 12 xcexcm;
(ii) not less than 90% (in terms of cumulative value based on the number of particles) of particles of not less than 3 xcexcm has a circularity xe2x80x9caxe2x80x9d of not less than 0.900 given by the following equation (1):
Circularity a=Lo/Lxe2x80x83xe2x80x83(1)
xe2x80x83[In the equation, Lo denotes a periphery length of a circle having the same projected area as a particle image and L denotes a periphery length of the particle image];
(iii) Relationship between a cut ratio Z and a weight mean size X of the above described toner fulfills the following equation (2):
Cut ratio Zxe2x89xa65.3xc3x97Xxe2x80x83xe2x80x83(2)
xe2x80x83[Incidentally, the cut ratio Z is a value calculated with a following equation (3):
Z=(1xe2x88x92B/A)xc3x97100xe2x80x83xe2x80x83(3)
xe2x80x83Wherein A is a particle density (the number of particles/xcexcl) of all measured particles measured with a flow type particle image analyzer and B is a particle density (the number of particles/xcexcl) of measured particles having a circular equivalent size of not less than 3 xcexcm]; and
(iv) Relationship between a cumulative value based on the number of particles Y of particles having a circularity of not less than 0.950 and a weight mean size X fulfills the following equation (4):
Yxe2x89xa7exp 5.51xc3x97Xxe2x88x920.641xe2x80x83xe2x80x83(4)
[Incidentally, the weight mean size X is 5.0 to 12.0 xcexcm]